Hot Big Bang from inflation without the inflaton reheating

According to the standard lore, a prolonged inflation leaves quantum field theory in cold, low entropy state. Thus, some mechanism is needed reheat this post-inflationary state, leaving hot, thermal, radiation-dominated Universe. Typically, reheating achieved coupling inflaton QFT degrees of freedom. We argue that nonequilibrium dynamics non-conformal (post-)inflationary background space-time can produce hot quark-gluon plasma with temperature order inflationary Hubble scale, without coupling.